Developments in cryptographic theory demonstrate how information theoretic secrecy can be generated from sources of joint randomness under the assumption that the potential attacker/eavesdropper does not significantly share the same source of randomness. These developments may be particularly well-suited for use in secrecy generation in wireless communication systems due to the nature of the wireless communication medium.
In order to communicate secretly, information-theoretic security could be used to protect communications between two terminuses, from being discovered by an attacker entity. Most wireless channels have a constantly changing physical property, which provides a lot of randomness on the terminus's channel observations. This is called this Joint Randomness Not Shared by Others (JRNSO) and is the subject of U.S. patent application Ser. No. 11/339,958.
In the prior art, JRNSO typically relies on two terminuses observing essentially the same Channel Impulse Response (CIR), a situation inherent to Time Division Duplex (TDD) where there is one reciprocal channel. Many communication systems however utilize Frequency Division Duplex (FDD), where two terminuses typically do not observe essentially the same channel impulse response due to the fact the signal transmission in each direction is on a significantly different channel frequency. Further, there is a need to make JRNSO based encryption in TDD applications more robust, and to expand JRNSO to environments which do not naturally produce sufficient JRNSO information. This could be due to the channel not being as close to true reciprocity as required for the application. These techniques are applicable to Single-Input-Single-Output (SISO) and Single-Input-Multiple-Output (SIMO) systems. Finally, there is a need to extend JRNSO to more sophisticated communication systems which use multiple-input-multiple-output (MIMO) or multiple-input-single-output (MISO) antenna arrays.